Heat oven to 350. Mix flour with 1/2 cup of the sugar in small bowl. Cut in 1/2 cup butter until resembles coarse crumbs. Press firmly into bottom of greased foil lined 13X9 baking pan. Bake 20 minutes or until edges are lightly browned. Microwave chocolate & remaining 1/2 cup butter in large microwaveproof bowl on high 1 1/2 minutes or until butter is melted. Stir until chocolate is completely melted.

Stir in syrup, remaining 1/2 cup sugar, eggs & vanill until well blended. Pour over crust. Sprinkle with nuts. Bake 30 minutes or until filling is set. Cool in pan. Cut into bars.